A conventional image record apparatus used with a monitoring camera system has a pre-record function of recording an image before an alarm occurs (for example, refer to Patent Document 1).
To perform pre-record, since the alarm occurrence timing is not previously known, an area of 8 MB (mega bytes)×integer, for example, is previously reserved in a record medium of a hard disk, etc., ad image data is recorded in the area. When an alarm occurs, the image data recorded so far in the reserved area is determined as the pre-record data.
Usually, a plurality of cameras are used in a monitoring camera system and thus the cameras and the image record apparatus are connected through a network of Ethernet (registered trademark), etc. The image record apparatus records an image sent from each camera in a record medium. Since the image sent from the camera is compressed, the image record apparatus does not grasp the image size until reception of the image from the camera.
The size of the area reserved for pre-record data is determined when the record medium is formatted. In the conventional image record apparatus, the area reserved for pre-record data is determined according to the following procedure:
(1) First, the size of one image is set to 512 kB and is multiplied by the pre-record rate and the pre-record time. That is, 512 kB×pre-record rate×pre-record time is calculated.
(2) The value calculated in (1) is rounded up so as to become a value of 8 MB×an integer. For example, when the pre-record rate is 5 ips (Image per second) and the pre-record time is 4 sec, the calculation result in (1) becomes 10.24 MB (512 kB×5 ips×4 sec).
(3) According to the result, 10.24 MB is rounded up to 16 MB and an area is reserved in the record medium.
Patent Document 1: JP-A-2005-151505